(a) Field of the Invention
The present invention relates to an improved connector for joining two tubular members together and has particular application for joining together shell portions forming a torpedo.
(b) Description of the Prior Art
A typical underwater vehicle such as a torpedo or the like is twenty one feet long and consists of five or more sections. The current method of joining vehicle sections together is by the use of joint bands, that is two semi-circular rings that are bolted together. This method, while mechanically efficient, tends to generate noise as water rushes by the crevasses between the sections, the joint band, and the bolt holes. This noise diminishes the effectiveness of the torpedo's listening capabilities. It also makes the vehicle more vulnerable to enemy detection. Consequently, there is a need for an improved method of joining the vehicle sections together.
Underwater vehicle shell sections are generally cylindrical in nature. In the prior art, there are a variety of different connectors for joining together tubular sections such as those of an underwater vehicle. U.S. Pat. No. 4,074,912 to Van Bilderbeek et al., U.S. Pat. No. 4,120,519 to Bridges and U.S. Pat. No. 4,477,104 to Akkerman illustrate some of the known connectors.
In the Van Bilderbeek et al. patent, a connector apparatus is illustrated which has particular utility in pile driving to enable a pile string to be released or disconnected in the vicinity of the mudline after the pile has been driven to its final depth. The connector includes an upper box secured to one portion of a pin apparatus attached by a releasable mechanism to another lower portion of the pin apparatus. Release of the mechanism is effected by a tool operated from a remote location. The release mechanism enables the drive pile string above the lower portion of the pin to be withdrawn through the water to the surface.
The Bridges patent illustrates a readily separable fastening structure for holding a pair of cylindrical sections together in axial alignment. The fastening structure includes annular rim members attached to inside surfaces near the end of the cylindrical sections, one of which has an outwardly extending flange spaced from the end of its corresponding cylindrical section to form an annular groove and the other of which is adapted to telescope within the first such rim member. The second rim member also includes an inwardly extending flange. A plurality of spaced members having spring fingers are attached to the outside of the second cylindrical section and extend beyond the end thereof. The spring fingers each have an inwardly extended ridge and a groove on the outside of the ridge. A small diameter cable is provided in the grooves. Tensioning members are included for pulling the cable tightly around the fingers to pull the inwardly extending ridges into the annular groove to lock the cylindrical members together. A pyrotechnic device is positioned to cut the cable to effect automated sequencing separation of the cylindrical sections.
The Akkerman patent discloses an apparatus for releasably latching the lower end of a tubing string within the bore of an upstanding well conduit by means of latching parts adapted to be received in latching position beneath a shoulder in the bore of the well conduit. The latching parts are locked in latching position by locking means which are engageable and releasable in response to manipulation of the well string. The latching parts are moved into unlatching position, upon release of the locking means, without the necessity of sliding contact between the latching parts and the shoulder. The latching parts include a circular array of disengageable fingers.
Shape memory alloys or smart alloys are also known in the art. They have been used in a variety of different applications because of their ability to change shape as a result of phase changes which occur during changes in their temperature. U.S. Pat. Nos. 4,281,841 to Kim et al., 4,778,074 to Kelly and 4,922,381 to Longerich et al. illustrate some of the applications for shape memory alloys.
More particularly, the Kim et al. patent relates to an all metal, reusable O-ring sealing arrangement for sealing two concentric tubes in an ultra-high vacuum system. The O-ring is formed from a heat recoverable alloy such as Nitinol and is concentrically positioned between protruding sealing rings of two concentric tubes. The O-ring is installed between the tubes while in a stressed martensitic state and is made to undergo a thermally induced transformation to an austenitic state. During the transformation, the O-ring expands outwardly and contracts inwardly toward a previously sized austenitic configuration, thereby sealing against the protruding sealing rings of the concentric tubes.
The Kelly patent relates to a composite material and metal canister having a cylindrical corrosion resistant metal shell and a composite material bulkhead within the shell which provides corrosion resistance and minimal weight coupled with the ability to withstand high internal pressures and bending stresses. The metal shell and the composite bulkhead are joined by a circumferential compression exerted on the shell by an external ring of shape memory material to produce a fluid-type seal therebetween the shell and an adjacent bulkhead.
The Longerich et al. patent is related to an electronics unit wherein a plurality of circular circuit cards are arranged in an aligned, parallel relationship. In this configuration, shape memory alloy rings are positioned around the outer peripheries of certain members to form a hermetic seal between certain regions or portions of the configuration. The shaped memory alloy is preferably selected such that the rings may be installed when at room temperature and then shrunk to form the hermetic seal as the rings are warmed by resistance heating to a predetermined temperatures.
None of these prior art patents however suggest using shape memory alloys as part of an easily releasable joint for joining sections of tubing or sections of a torpedo outer shell together.